<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" id="viewport" content="width=375,initial-scale=1,user-scalable=0">
    <style>
        div{
            width: 100px;
            height: 100px;
            /*border: solid 2px red;*/
            margin-bottom: 10px;
        }
        .div1{
            background: url(img/icon@3x.png) 0 0 no-repeat;
        }
        .div2{
            background: url(img/icon.png) 0 0 no-repeat;
            background-image: -webkit-image-set(url(img/icon.png) 1x,url(img/icon@2x.png) 2x);
        }
        .div3{
            background: url(img/icon@3x.png) 0 0 no-repeat;
            background-image: -webkit-image-set(url(img/icon.png) 1x,url(img/icon@2x.png) 2x,url(img/icon@3x.png) 3x);
        }

    </style>
</head>
<body>
    <!--retina  2倍 或者 3倍的屏幕-->

    <div class="div1"></div>
    <div class="div2"></div>
    <div class="div3"></div>

    <img src="img/icon.png" alt="">
    <img src="img/icon.png" srcset="img/icon@2x.png 2x" alt="">
</body>
</html>